BUFFER AND HYDROLYSIS

BUFFER SOLUTION

1

Components of acidic buffer solution are ... and ...

weak acid and its conjugate base

1

The conjugate acid and base of H₂O are ... and ... respectively.

conjugate acid H₃O⁺

conjugate base OH^-

1

The uses of buffer solution is ...

Maintain a stable pH in various applications

1

In acid-base reaction, based on Bronsted-Lowry's theory, the proton is transferred from ...... to ....

from acid to base

pH value of buffer solution

2

Given that 100 ml NH₃ 0.04 M is added to 200 ml (NH₄)₂SO₄ 0.01 M. Kb NH3 = 5 x 10 ^-5

Find the pH value of the mixture!

Basic buffer ( weak base and its conjugate acid)

mol NH3 = 0.1 x 0.04 = 0.004 mol

mol (NH₄)₂SO₄ = 0.2 x 0.01= 0.002 mol

[OH-]=5 x 10 ^-5 x( 0.004 : (0.002 x 2)) = 5 x 10 ^-5

 pOH = 5 - log 5

pH = 9 + log 5

pH value of buffer solution

1

A 6-gram CH₃COOH is added into 200 ml CH₃COONa 0.02 M. Mr CH₃COOH =60. Ka CH₃COOH= 10^-5

Find the pH value of the mixture!

mol CH₃COOH = 6 : 60 = 0.1 mol

mol CH₃COONa = 0.2 x 0.02 = 0.004

[H⁺] = 10^-5 x (0.1 : 0.004) =2.5 x 10 ^-4

pH = 4 - log 2.5

2

At STP, a 224 ml NH₃ gas is bubbled into 100 ml (NH₄)₂SO₄ 0.02 M. Kb = 5 x 10 ^-5

Find the pH value of the buffer solution!

Mol NH₃ = 0.224 : 22.4 = 0.01 mol

Mol ammonium sulfate = 0.1 x 0.02 = 0.002

[OH^-]=5 x 10 ^-5x(( 0.01 : 0.002 x 2))= 1.25 x 10^-4

pOH = 4 - log 1.25

pH = 10 + log 1.25

HYDROLYSIS

2

Write the hydrolysis reaction of (CH₃COO)₂Mg

(CH₃COO)₂Mg -> CH₃COO^-  + Mg⁺²

CH₃COO^- + H₂O -> CH₃COOH + OH-

 Mg⁺²  + H₂O ->  Mg(OH)₂ + H⁺

PH OF SALT

1

Determine the pH value of 100 ml CH₃COONa 0.04 M, Ka = 4 x 10^-6

Basic salt 

[OH-]=((10^-14x0.04x1) : (4x10^-6))^1/2=10^-5

pOH = 5

pH = 9

2

A-1.32 grams of (NH₄)₂SO₄ is dissolved in 2 L of water. Find the pH value of the solution if Kb NH₃=10^-5

mol of salt = 1.32 : 132 = 0.01 mol

[salt] = 0.01 : 2= 0.005 M

Acidic salt

[H⁺]=((10^-14x0.005x2) : (10^-5))^1/2=10^-4.5

pH = 4.5